This invention relates generally to electric motors and more particularly to an electric motor having a simplified, easily assembled construction.
Assembly of electric motors requires that a rotor be mounted for rotation relative to a stator so that magnets on the rotor are generally aligned with one or more windings on the stator. Conventionally, this is done by mounting a shaft of the rotor on a frame which is attached to the stator. The shaft is received through the stator so that it rotates about the axis of the stator. The frame or a separate shell may be provided to enclose the stator and rotor. In addition to these basic motor components, control components are also assembled. An electrically commutated motor may have a printed-circuit board mounting various components. Assembly of the motor requires electrical connection of the circuit board components to the winding and also providing for electrical connection to an exterior power source. The circuit board itself is secured in place, typically by an attachment to the stator with fasteners, or by welding, soldering or bonding. Many of these steps are carried out manually and have significant associated material labor costs. The fasteners, and any other materials used solely for connection, are all additional parts having their own associated costs and time needed for assembly.
Tolerances of the component parts of the electric motor must be controlled so that in all of the assembled motors, the rotor is free to rotate relative to the stator without contacting the stator. A small air gap between the stator and the magnets on the rotor is preferred for promoting the transfer of magnetic flux between the rotor and stator, while permitting the rotor to rotate. The tolerances in the dimensions of several components may have an effect on the size of the air gap. The tolerances of these components are additive so that the size of the air gap may have to be larger than desirable to assure that the rotor will remain free to rotate in all of the motors assembled. The number of components which affect the size of the air gap can vary, depending upon the configuration of the motor.
Motors are commonly programmed to operate in certain ways desired by the end user of the motor. For instance certain operational parameters may be programmed into the printed circuit board components, such as speed of the motor, delay prior to start of the motor, and other parameters. Mass produced motors are most commonly programmed in the same way prior to final assembly and are not capable of re-programming following assembly. However, the end users of the motor sometimes have different requirements for operation of the motor. In addition, the end user may change the desired operational parameters of the motor. For this reason, large inventories of motors, or at least programmable circuit boards, are kept to satisfy the myriad of applications.
Electric motors have myriad applications, including those which require the motor to work in the presence of water. Water is detrimental to the operation and life of the motor, and it is vital to keep the stator and control circuitry free of accumulations of water. It is well known to make the stator and other components water proof. However, for mass produced motors it is imperative that the cost of preventing water from entering and accumulating in the motor be kept to a minimum. An additional concern when the motor is used in the area of refrigeration is the formation of ice on the motor. Not uncommonly the motor will be disconnected from its power source, or damaged by the formation of ice on electrical connectors plugged into the circuit board. Ice which forms between the printed circuit board at the plug-in connector can push the connector away from the printed circuit board, causing disconnection, or breakage of the board or the connector.